1. Field of the Invention
The present invention relates to a rectifier in alternating current generators for automotive vehicles.
2. Description of the Prior Art
Generally, alternating current generators for automotive vehicles such as cars, buses, trucks, motorcycles and the like include a core shaft or rotary shaft, a rotor core such as Lundell type one fitted to the core shaft, a coil bobbin incorporated in the rotor core, a rotor coil wound around the rotor core, a stator, a stator coil wound around the stator, a plurality of brushes, a brush holder, a plurality of slip rings, a rectifier which rectifies generated alternating current into direct current, and a cooling fan provided on the rotor core for cooling the rectifier, the rectifier being positioned in air course in which air for cooling the radiator is introduced into the inside of the generator from the outside of the casing of the generator by the action of the cooling fan.
Since the radiator generates or releases a considerable amount of heat upon rectification it must be cooled as much as possible to improve the efficiency thereof, and for this purpose provision of radiators with cooling fins has been proposed and successful to some extent.
An example of conventional rectifier is of a structure such that a positive-side diode and a negative side diode are attached to a molded substrate both the sides of which are provided with cooling fins so as to project therefrom as described, for example, in Japanese Utility Model Application Laid Open No. Sho-58-75479. However, the conventional construction is disadvantageous in that the efficiency of cooling is unsatisfactory although cooling fins are provided on the substrate. It is difficult to increase the size of the substrate since various electric or electronic devices are used in the automotive vehicle, which reduces the space available for the enlargement of the substrate.
Examples of conventional rectifier including split type radiators are described, for example, in U.S. Pat. Nos. 4,488,070 and 4,419,597. The rectifier described in U.S. Pat. No. 4,488,070 is comprised by a pair of radiators, one for positive side and the other for negative side arranged in parallel relation to each other on the inner and outer diameter sides, having embedded therein a plurality of diodes for positive and negative electrodes, respectively, and provided with cooling fins, with lead wires from the diodes and output side lead wire from a stator coil being soldered to a terminal board or strip embedded in an insulating substrate. This approach has been successful to some extent. However, with view to meeting with recent demands of reducing the weight and volume of the apparatus as well as obtaining a higher output generator, it is now desired strongly to improve the efficiency of cooling the radiators in the rectifier by the employment of larger fins.
Further, diodes which are arranged in a juxtaposed fashion on the radiator tend to stand at different temperatures upon rectification depending on their utility or function in the rectifying circuit and therefore there tends to be observed fluctuation in the distribution of the temperature of the radiator, resulting in that the diodes do not operate in a uniform fashion, thus failing to provide rectifiers having satisfactory reliability.
Conventionally, in rectifiers, positive and negative side radiators are assembled by means of a plurality of bolts so that they can be disposed in superposed relation, with the terminal ends being secured by the bolts to a case bracket of the generator, as shown in FIG. 5. More particularly, one of the radiators, say radiator 16, together with a terminal bar 23 is fixedly engaged with a first bolt 13 in a serration contact at one end thereof and the other end thereof is movably engaged with a second bolt 13' whereas the other radiator 15 is movably engaged with the first bolt 13 at one end thereof and fixedly engaged with the second bolt 13' in a serration contact at the other end thereof. This type of the conventional construction is disadvantageous in that one of the terminal ends of the radiator 16 is not secured fixedly by the bolt with the result that when the radiator 16 is attached or fitted to the case bracket the terminal end movably or rotatably engaged with the bolt 13' tends to be distorted to exert a residual stress on diode chips embedded in the radiator 16 in the direction indicated by arrow in FIG. 5. This would cause loss of the diode chips, breakage of lead wires from the diode chips, peeling of solder used for fixing the diode chips or the like troubles. In this respect, too, further improvement in the structure of rectifiers is desired.
Moreover, the conventional rectifiers include radiators provided with diode chips and an insulating substrate opposing or facing the radiators, the insulating substrate having provided therewith a plurality of terminal boards, each of which is connected to a terminal or foot extending from the corresponding diode chip and a lead wire from a stator coil. Since the terminal board is composed of a single plate onto which the terminal of the diode chip and the lead wire from the stator coil are connected at the same position heat applied upon connecting or external stress exerted from the side of the stator coil tend to be transmitted through the single terminal board to the diode chip which is susceptible to such heat and stress. This also causes various inconveniences described above and thus ultimately deteriorates the reliability of the rectifier.